Cooking Appliance, Especially Top-Mounted Cooking Appliance, and Method for Controlling a Cooking Appliance

ABSTRACT

A cooking appliance, especially a top-mounted cooking appliance including a muffle that defines a cooking space and is provided with a muffle access opening; a door pivotably mounted to the muffle for movement into and our of a covering relation with the access opening; a driving device in operative engagement with the door; a control device operatively associate with the driving device for controlling door movement; and an arrangement for determining a door displacement parameter during door movement, wherein a determined door displacement parameter is used as a reference parameter for a function of the appliance.

The invention relates to a cooking appliance, particularly a top-mountedcooking appliance, comprising at least a muffle that delimits a cookingspace, and is provided with a muffle hole, a door for closing the mufflehole and a driving device which is controlled by a control device and isused for displacing the door.

A top-mounted cooking appliance is known from DE 102 28 140 A1 in whichthe jamming of objects by the bottom door may be detected by a pluralityof anti-jamming switches that may be actuated independently of oneanother and are located between the bottom door and the muffle frame. Inaddition, any pressure increase may be evaluated in a door seal with ahollow cross-section.

In DE 101 64 239 A1, an anti-jamming mechanism is described which istriggered by varying tensile forces on the traction cables driving thebottom door. A torque sensor is also described, which registers a loadmoment on the drive shaft of an electric motor. Tensile force sensors,piezoelectric sensors and deformation or tension/expansion sensors arelisted as sensors for this purpose.

DE 102 88 141 A1 also describes an optoelectronic sensor for detecting ajam, which is activated by the quantity of reflected light.

The disadvantage of the described jam detectors is that they are eitherrelatively slow (tensile force sensors), or imprecise and prone to error(optical force sensors) and, furthermore, require increased installationcosts.

The main disadvantage is that the function for detecting a jammed objectdoes not work reliably, if at all, if there is a variation in theinternal parameters of the cooking appliance itself or in externalfactors. For example, a heavy load on the door may mean that a presetdisplacement speed cannot be achieved, or can only be achieved after adelay. Furthermore, using the cooking appliance in an area where thevoltage fluctuates between too high and too low may result in short-termdeviations. Finally, the effects of aging on the drive for the door oron guide rails may mean that an originally preset displacement speed canno longer be reached.

Another disadvantage is a triggering of a closing process for the door,in which—shortly before the closed state is reached—there is achangeover from an anti-jamming mechanism in which a switch or afunction is used for detecting a jammed state, to a closing mechanismfor registering a closed state.

The object of the invention is, therefore, to provide rapid, simple andprecise adjustment of the cooking appliance to variable operatingconditions, and—preferably—a displacement speed detector for a cookingappliance of the type described above.

This object is achieved by the cooking appliance having the featuresdescribed in claim 1 and by a method according to claim 9.

Thus a cooking appliance is preferred, particularly a top-mountedcooking appliance, comprising at least a muffle that delimits a cookingspace, and is provided with a muffle hole, a door for closing the mufflehole and a driving device which is controlled by a control device and isused for displacing the door, wherein—during a displacement of thedoor—a parameter that is dependent upon said displacement of the door isdetected and wherein the detected parameter is used as the referenceparameter for a function of the appliance.

In this way the cooking appliance and its functionalities may beadvantageously adjusted to local or current operating conditions. Thiswould enable environmental influences, as well as a non-standardoperating voltage or a varying load on the door, to be taken intoaccount as external operating conditions. Internal operating conditionsthat may be taken into account include, for example, effects of aging ofthe cooking appliance itself, for example an aging drive motor or wearon guide rails for displacement of the door, so that even gradualchanges such as the effects of friction may be taken into account.

The reference parameter is thus advantageously always approximated asclosely as possible to an actual target value. As well as aspeed-dependent reference parameter being taken into account, the lattermay also be determined on the basis of other variable factors such as amotor current.

The reference parameter may subsequently be used as a criterion for thetriggering of a function in the same displacement movement of the door.This advantageously enables a respective adjustment in particular of thedisplacement speed and—for example—of an anti-jamming mechanism, sothat, for example, a varying load on the door may be taken into accountindividually for the respective displacement cycle.

The reference parameter may also subsequently be used as a criterion insubsequent displacement movements of the door. The settings for basicparameters or for basic parameter ranges can thereby advantageously bedefined when the cooking appliance is commissioned for the first time,or at periodic intervals during maintenance activities. In addition tothe initial memorization of functions, this also enables the parametersthus defined to be adjusted from time to time so that even gradualchanges, for example elevation speed, can be taken into account on thebasis of changing frictional conditions.

A reference speed determined from a displacement speed may be defined asthe reference parameter. The reference parameter is preferablydetermined for this purpose after a constant displacement speed has beenreached. This enables the parameter to be determined reliably during aninitial acceleration phase without load-dependent acceleration effects.The reference parameter may also be determined, however, after aconstant acceleration has been achieved. This enables the parameter tobe set at particularly early stage, so that it may be used particularlyadvantageously for the current displacement movement.

The determination of the reference parameter is alternatively definedover the entire displacement path or part thereof, e.g. it is initiallydetermined and then subsequently adjusted to favorable effect. Such anapproach offers the advantage of, for example, enabling frictionaleffects from lifting rails and similar to be detected especiallyaccurately and to be taken into account.

A jammed state may therefore advantageously be determined dependent uponthe defined reference parameter. This ensures the correct functioning ofsafety-related functions, such as the detection of a jammed state evenin variable environmental conditions, for example where the operatingvoltage is too high or too low, resulting in fluctuations indisplacement speed.

The reference parameter is determined preferably by keeping a buttonpressed down, or—in particular—two buttons (e.g. displacement buttons)to be operated with both hands. If the buttons are released early, theprocess to determine the reference parameter is preferably aborted. Sucha procedure is useful since, if the process is aborted early due to therelease of the displacement buttons or other buttons, this prevents areference parameter value being determined on the basis of an erroneousdisplacement process. Automatic operation on the basis of the parameteror reference parameter to be determined, e.g. an automatic displacementoperation, is then conveniently not possible.

For this purpose, the cooking appliance—which is, in particular, atop-mounted cooking appliance but may also be a cooking appliance withan oven carriage—is equipped with a speed measurement device fordetermining a displacement speed of the door. The speed measurementdevice enables an object jammed by the door to be detected by monitoringof the displacement speed, wherein the displacement movement does notneed to be speed-controlled, but may—for example—also be governed on aload-dependent basis via the motor voltage or motor current. Thedisplacement movement of the door is, however, advantageously alsocontrolled on a speed-dependent—and therefore also load-dependent—basis,e.g. via a central control unit.

It is particularly advantageous, for the closure case, if at least oneend switch is available in addition, said end switch being disposedbetween muffle hole and/or frame, and door, wherein any activation of atleast one end switch deactivates the anti-jamming device or a first typeof anti-jamming mechanism, and thus terminates protective measures. Thisend switch preferably activates with an degree of opening of less thanone centimeter, in particular in a range of 4-9 mm, which is so smallthat no normal household objects could become jammed. If at least oneend switch is activated the door is pushed with defined force—and nolonger with controlled speed—onto the muffle hole. Nevertheless, it isadvantageously guaranteed that the door is not unintentionally reversedon closing, but can still be reversed if an object should become jammedin the final phase of closing.

In particular, the non-abrupt, premature stopping of the closuremovement would indicate that a child's finger has become jammed, inwhich case the door is immediately opened again, particularly to adegree sufficient to allow the finger to be withdrawn. Such non-abrupt,premature stopping of the closure movement may be detected withparticular reliability by the monitoring of a speed differential value.

However, in order to prevent even smaller objects, or—in particular—achild's finger, from becoming jammed, it is preferable for a switchoverto a modified safety feature to be provided instead of completedeactivation.

The advantage of this speed-supported anti-jamming device is that isresponds relatively quickly, can hold accurate input date, and may beimplemented relatively easily without major design measures.

The monitoring of the displacement speed can be focused on a reductionin the displacement speed, which is uncontrolled and therefore cannot bedeliberately regulated. This may occur in that a value measured by thespeed measurement device deviates from a target value by a fixed orpercentage value. If the deviation is above or below a defined thresholdvalue, a jam is assumed to have occurred. For example, if the door canno longer be displaced with the set target speed because an object ispreventing it from doing so, then its speed is reduced accordingly. Thisevaluation and monitoring may be carried out—for example—in a centralcontrol device, e.g. via suitable microcontrollers.

Alternatively, or additionally, a timing-related change in thedisplacement speed—especially too rapid a change—may trigger a jamsituation, if—for example—the door slows down more quickly than providedfor, in the event of a jam.

The values are, of course, selected such that jam situations are nottriggered by speed fluctuations caused by the normal process for thedisplacement of the door. In addition, the anti-jamming methodsdescribed in the prior art, such as motor current measurement, may alsobe used.

It is advantageous for the speed measurement device to comprise at leastone sensor on a motor shaft of the drive mechanism, in particular adrive motor, by which corresponding sensor signals can be generated uponrotation of said motor shaft. This facilitates a relatively rapidresponse. The sensor signals are directly or indirectly a measure of thedisplacement speed of the door. It is then particularly beneficial if atleast one sensor is a Hall sensor which emits two sensor signals permotor shaft rotation. The Hall sensor system is easy to install, fastand non-sensitive. Two (partial) Hall elements are advantageouslyattached to the motor shaft, so that two signals are emitted for eachrotation of the motor shaft. Evaluation of the timing of these signalsenables a speed to be determined for the bottom door, for example viacomparison tables or by conversion to real time. The displacement speedis preferably detected by a time differential between the sensorsignals.

In order to determine a stable speed it is advantageous for several,i.e. more than two, sensor signals to be evaluated. To this end it isalso advantageous if several, i.e. more than two, sensor signals, areemitted.

It is particularly advantageous if the displacement direction of thedoor is reversed once the jam has been detected.

For this purpose an anti-jamming device may be provided which monitorsfor jam situations and/or implements any measures to be carried out inthe event of a jam. The anti-jamming device may be a separate device orfunctionally integrated into existing control circuits, e.g. into thecentral control circuit or into a control board or lift board.

It is preferable for the anti-jamming system or the anti-jamming deviceto be activatable only if a target displacement value, in particular atarget speed, is reached by the door. This minimizes the risk of theanti-jamming mechanism being triggered incorrectly.

In order to protect the object jammed by the door, it is advantageous ifa maximum force-time curve is not exceeded by the door. Jammed “by” thedoor may mean jammed between the door and an outer limit, e.g. the worksurface, or jammed between door and muffle frame or housing. Differentforce-time curves may be provided for each case.

It is particularly advantageous, for the closure case, if at least oneend switch is available in addition, which is disposed in the areabetween muffle hole or frame and door, wherein any activation of atleast one end switch deactivates the anti-jamming device or anti-jammingmechanism, i.e. interrupts protective measures. This end switchtypically activates with a degree of opening of 4-9 mm, which is sosmall that no objects could still be jammed. On the other hand, thisguarantees that the door is not unintentionally reversed on closing. Ifthe at least one end switch is activated, the door is pushed withdefined force—and no longer with controlled speed—onto the muffle hole.

The speed measurement device may, however, also be used for otherpurposes, such as setting the displacement speed of the door. This aloneis not yet known and also is not obvious.

The invention is particularly suitable for top-mounted cookingappliances in which the muffle hole is at the bottom and the door is abottom door, which preferably moves in linear fashion.

The invention is described in greater detail below on the basis of theattached schematic diagrams, in which:

FIG. 1 shows a perspective view of a wall-mounted, top-mounted cookingappliance with bottom door lowered;

FIG. 2 shows a perspective view of the top-mounted cooking appliancewith bottom door closed;

FIG. 3 shows a perspective view of a housing of the top-mounted cookingappliance without the bottom door;

FIG. 4 shows a schematic side view in cross-section along the line I-Ifrom FIG. 1 of the wall-mounted, top-mounted cooking appliance withbottom door lowered;

FIG. 5 shows the front view of a further embodiment of a top-mountedcooking appliance;

FIGS. 6 to 11 are diagrams of displacement movements of a bottom doorunder various basic conditions;

FIGS. 12 and 13 are force-time profile curves for a bottom door; and

FIG. 14 is a diagram of a preferred displacement movement when a thinobject is jammed between a bottom door and a muffle.

FIG. 1 shows a top-mounted cooking appliance with a housing 1. The rearside of the housing 1 is attached to a wall 2 in the manner of a hangingcupboard. A cooking space 3 is delimited in the housing 1, which may bemonitored through a viewing window 4 set into the front face of thehousing 1. FIG. 4 shows that the cooking space 3 is delimited by amuffle 5, which is provided with a heat-insulating sheathing (notillustrated), and that the muffle 5 has a muffle hole 6 in the bottomsurface. The muffle hole 6 can be closed with a bottom door 7. In FIG. 1the bottom door 7 is shown in a lowered state, wherein it lies with itsunderside on a work surface 8 of a kitchen appliance. In order to closethe cooking space 3, the bottom door 7 must be adjusted to the positionshown in FIG. 2, known as the “zero position”. For the purpose ofadjusting the bottom door 7 the top-mounted cooking appliance has adrive mechanism 9, 10. The drive mechanism 9, 10 has a drive motor 9,shown by dashed lines in FIGS. 1, 2 and 4, which is disposed between themuffle 5 and an outer wall of the housing 1. The drive motor 9 isdisposed in the area of the rear face of the housing 1, and—as shown inFIG. 1 or 4—is effectively connected to a pair of lifting elements 10,which are connected to the bottom door 7. According to the schematiclateral view from FIG. 4 each lifting element 10 is designed as anL-shaped carrier, whereof the horizontal legs extend out from the drivemotor 9 on the housing side. In order to adjust the bottom door 7 thedrive motor 9 may be activated with the help of an operating panel 12und and a control circuit 13, which are disposed on the front surface ofthe bottom door 7 in accordance with FIGS. 1 and 2. As shown in FIG. 4,the control circuit 13 is located behind the operating panel 12 insidethe bottom door 7. The control circuit 13, which is assembled in thiscase from several spatially and functionally separate PCBs thatcommunicate via a communication bus, is a central control unit foroperating the appliance and controls and/or regulates functions such asheating up, displacement of the bottom door 3, implementation of userinputs, illumination, an anti-jamming mechanism, timing of the heatingelements 16, 17, 18, 22, and much more.

FIG. 1 indicates that an upper surface of the bottom door 7 has acooking hob 15. Almost the entire surface of the cooking hob 15 isoccupied by heating elements 16, 17, 18, which are shown in FIG. 1 bydashed lines. In FIG. 1 the heating elements 16, 17 are two separatecooking zone heating elements of different sizes, whilst the heatingelement 18 is a flat heating element provided between the two cookingzone heating elements 16, 17 that virtually surrounds the cooking zoneheating elements 16, 17. The cooking zone heating elements 16, 17 definerelevant cooking zones or hobs for the user; the cooking zone heatingelements 16, 17 together with the flat heating element 18, define anunder-surface heating zone. The zones may be indicated by an appropriatedécor on the upper surface. The heating elements 16, 17, 18 can each becontrolled via the control circuit 13.

In the exemplary embodiment shown, the heating elements 16, 17, 18 aredesigned as radiant heating elements which are covered by a vitroceramicplate 19. The vitroceramic plate 19 has roughly the same dimensions asthe upper surface of the bottom door 7. The vitroceramic plate 19 is,furthermore, equipped with mounting holes (not illustrated), throughwhich extend bases for supporting the retaining parts 20 for cookingproduct carriers 21, as also shown in FIG. 4. Other—preferably readilyappealing—covers may also be used instead of a vitroceramic plate 19,e.g. a thin metal sheet.

With the help of an operating handle provided in the operating panel 12,the top-mounted cooking appliance may be switched to hob orunder-surface heating mode, as explained below.

In hob mode the cooking zone heating elements 16, 17 are triggeredindividually via the control circuit 13 by means of operating elements11, which are provided in the operating panel 12, whilst the flatheating elements 18 remain out of operation. The hob operating mode maybe executed with the bottom door 7 lowered as shown in FIG. 1. It may,however, also be operated with the cooking space 3 closed, with thebottom door 7 raised up in an energy-saving function.

In under-surface heating mode, not only the cooking zone heatingelements 16, 17 but also the flat heating elements 18 are triggered bythe control device 13.

To ensure that the cooking product is browned as evenly as possibleduring under-surface heating mode, it is crucial that the cooking hob 15providing the heat from below has equal distribution of the heat outputover the surface of the cooking hob 15, even though the heating elements16, 17, 18 have different nominal outputs. Thus the heating elements 16,17, 18 are advantageously not switched to continuous operation by thecontrol circuit 13, but the power supply to the heating elements 16, 17,18 is delivered at timed intervals. This means that the differentnominal heat outputs of the heating elements 16, 17, 18 are reducedindividually so that the heating elements 16, 17, 18 achieve an evendistribution of heat output across the surface of the cooking hob 15.

FIG. 4 is a schematic diagram showing the position of a fan 23, e.g. forgenerating circulating area in a hot-air mode or for supplying cool air.In addition, an upper heating element 22, which is attached to an upperside of the muffle 5, is provided, which may be designed with one ormore rings, e.g. with an inner and an outer ring. Further heatingelements, such as a ring element, may also be provided between the rearwall of the housing 1 and the muffle, though such heating elements arenot illustrated here for the sake of clarity. The control circuit 13 maybe used for setting the various operating modes, such as—for example—topheating, hot-air or rapid heating mode, by appropriate actuation andsetting of the heating output of the heating elements 16, 17, 18, 22,with activation of the fan 23 if necessary. The heating output may beadjusted by means of a suitable timed delivery system. In addition thecooking hob 15 may have a different design, e.g. with or withoutgrilling zone, as a single or multi-ring warming area without hob, andso on. The housing 1 has a seal 24 to the bottom door 7.

The operating panel 12 is arranged mainly on the front face of thebottom door 7. Alternatively, other arrangements are also possible, e.g.on the front face of the housing 1, distributed across differentsubpanels and/or partially on the lateral surfaces of the cookingappliance. Other designs are possible. The operating elements 11 areunrestricted in terms of their construction and may take the form of,for example, operating handles, toggle switches, push-buttons ormembrane keys, which incorporate display elements 14 such as—forexample—LED, LCD and/or touchscreen displays.

FIG. 5 is a schematic, not-to-scale diagram of a top-mounted cookingappliance drawn from the front, in which the bottom door 7 is opened andresting on the work surface 8. The closed state is drawn in dashedlines.

In this embodiment, two displacement switch panels 25 are located on thefront face of the permanently mounted housing 1. Each displacementswitch panel 25 comprises two push-buttons, namely an upper CLOSE button25 a for displacing the bottom door 7 upward in the closing direction,and a lower OPEN button 25 b for displacing the bottom door 7 downwardin the opening direction. Without automatic operation (see below) thebottom door 7 is displaced upward only by continuous, simultaneouspressure on the CLOSE buttons 25 a of both displacement switch panels25, if possible; the bottom door 7 is likewise also displaced downwardonly by continuous, simultaneous pressure on the OPEN buttons 25 b ofboth displacement switch panels 25, is possible (manual operation).Since manual operation requires increased attention by the user duringoperation and, in this case, also requires the use of both hands, ananti-jamming mechanism is merely optional. In an alternative embodiment,displacement switch panels 26 are located on opposite outer surfaces ofthe housing 1 with corresponding CLOSE buttons 26 a and OPEN buttons 26b, as indicated by the dotted lines.

The control circuit 13, which is shown by a hatched line on the interiorof the bottom door 7 behind the operating panel 12, actuates the drivemotor 9 so that the bottom door 7 begins to move gently, i.e. notabruptly by the drive motor 9 simply being started up, but by means of adefined ramp.

In this exemplary embodiment the control circuit 13 comprises a memoryunit 27 for storing at least one destination or displacement positionP0, PE, P1, P2, PZ of the bottom door 7, preferably with volatile memorycomponents, e.g. DRAMs. If a destination position P0, P1, P2, PZ isstored, then the bottom door—after actuation of one of the buttons 25 a,25 b or 26 a, 26 b on the displacement switch panels 25 or26—automatically moves in the set direction until the next destinationposition is reached or one of the buttons 25 a, 25 b or 26 a, 26 b isactuated again (automatic operation). In this exemplary embodiment thelowest destination position PZ corresponds to the maximum open state,the (zero) position P0 corresponds to the closed state, and P1 and P2are freely adjustable positions in between. Once the last destinationposition is reached for a direction, manual operation must be used forfurther displacement if this is possible (i.e. the final end positionsdo not correspond to the maximum open or closed end state). In the sameway, if no destination position is stored for a direction—as would bethe case, for example, for an upward movement to the closed position ifonly PZ is stored, but not P0, P1, P2, then manual operation must beused. If no destination position is stored, e.g. for a new installationor after a power outage, automatic operation is not possible. If thebottom door 7 is displaced, particularly in automatic mode, then ananti-jamming mechanism is preferably activated.

Automatic operation and manual operation are not mutually exclusive:continuous activation of the displacement switch panel(s) 25, 26 alsocauses the bottom door 7 to move in manual mode, if a destinationposition could be reached in this direction. In this case, for example,a maximum actuation time of e.g. 0.4 seconds for the displacement panels25 or 26, or—more precisely—for the corresponding buttons 25 a, 25 b or26 a, 26 b, may be set for activation of the automatic mode.

A destination position P0, P1, P2, PZ may be any position of the bottomdoor 7 between and including the zero position P0 and the maximum openposition PZ. The maximum stored open position PZ need not, however, bethe position resting on the work surface 8. The destination positionsP0, P1, P2, PZ may be stored with the bottom door 7 at the requireddestination position P0, P1, P2, PZ, by pressing an actuation button 28in the operating panel 12—for example—for several seconds (e.g. twoseconds continuously). Existing optical and/or acoustic signal emitters,which emit appropriate signals when a destination position is stored,are not drawn for the sake of clarity. The required destination positionP0, P1, P2, PZ to be set is reached—in this exemplary embodiment, forexample—by operating the displacement switch panels 25 or 26 with bothhands and manual displacement to this position.

Just one destination position, or—as shown in this exemplaryembodiment—a plurality of destination positions P0, P1, P2, PZ, may bestored in the memory unit 27. If there is a plurality of destinationpositions P0, P1, P2, PZ these may be reached in succession by actuationof the corresponding displacement buttons 25 a, 25 b or 26 a, 26 b.Using a plurality of destination positions P0, P1, P2, PZ thetop-mounted cooking appliance can easily be adjusted to the requiredoperating height of several users. The destination position(s) mayadvantageously be canceled and/or overwritten. In one embodiment, forexample, only one destination position may be stored in the open state,whilst the zero position P0 is automatically detected and can beautomatically reached. Alternatively, the zero position P0 must also bestored in order to be automatically accessible.

It is particularly beneficial, in the interests of ergonomic use, forone or more of the destination positions P1, P2, PZ to open the bottomdoor 7 by at least approx. 400 mm to approx. 540 mm (i.e. P1-P0, P2-P0,PZ-P0>40 cm to 54 cm). With this degree of opening the cooking productcarriers 21 can easily be placed in the retaining parts 20. In thisinstance it is beneficial if the viewing window 4 is set approximatelyat the user's eye level or slightly below, e.g. by means of a templateindicating the size of the cooking appliance.

The diagrams do not show an existing mains power buffering for bridgingpower outages of approx. 1 to 3 seconds, and preferably up to 1.5seconds of power outage.

The drive motor 9 from FIG. 1 has at least one sensor unit 31, 32 on amotor shaft 30, arranged either in front or behind a gear unit, in orderto measure a displacement path or a position and/or a speed for thebottom door 7. The sensor unit may, for example, comprise one or moreinduction, Hall, optical or SAW sensors, etc. In this case, for simplemeasurement of path and speed, two Hall (partial) elements 31 aremounted on the motor shaft 30, offset by 180°—i.e. opposite oneanother—and a Hall meter 32 is installed at a fixed location in thisarea, at a distance from the motor shaft. If a Hall element 31 thentravels past the meter 32 when the motor shaft 30 rotates, a measurementand/or sensor signal is generated that is, in good approximation,digital. Therefore, with (for example) two Hall elements 31, a rotationof the motor shaft 30 causes two signals to be emitted. If the timing ofthese signals is analyzed, e.g. the difference in time between them,then the speed vL of the bottom door 7 can be determined, for examplevia comparison tables or by conversion into real time in the controlcircuit 13. By addition or subtraction of the measurement signals, adisplacement path or position for the bottom door 7 may be determined.

A speed regulator may implement the speed, for example by means of aPWM-controlled power semiconductor.

In order to determine the zero point, the path measurement isautomatically readjusted at each actuation by initialization of thebottom door 7 in the zero position P0, so that—for example—an erroneoussensor output or recording is not implemented.

The drive motor 9 can be operated by actuation of both displacementswitch panels 25 or 26 even if the main switch 29 is deactivated.

Instead of two separate switches for each displacement panel 25, 26, asingle switch for each displacement panel is also possible, e.g. atoggle switch with neutral position, which actuates only under pressure.Other forms are also possible. Nor are the operating elements 28, 29 onthe operating panel 12 restricted as to their type and arrangement.

The arrangement and distribution of the control circuit 13 is thusflexible and not restricted, and may therefore also comprise a pluralityof PCBs, e.g. a display board, a control board and a lift board, whichare spatially separate.

A 4-mm opening, for example, may be detected by end switches 33, whichdeactivate an anti-jamming mechanism upon actuation. Deactivation of theanti-jamming mechanism may, however, also be possible for example bycounting pulses from the sensor signals, when a count value is reachedwhich corresponds to a final measurement of—for example—8.6 mm.

The anti-jamming mechanism is thus deactivated independently of suchmechanical end switches 33.

The top-mounted cooking appliance may also be designed without a memoryunit 27, in which case automatic operation is not possible. This may beuseful for increasing user safety, e.g. protection against jamming.

FIG. 6 is a not-to-scale diagram showing application of the displacementspeed vL of the bottom door 7 in mm/s compared to the position of thebottom door in mm from the zero position P0 for a displacement of thebottom door 7 from the closed state where P0=0 mm to PZ=maximum opening,in this case 530 mm in manual displacement mode (i.e. without automaticdisplacement), and, as indicated by the dotted arrow, a stopping of thedisplacement movements between P0 and PZ. The curve will run in thedirection of the arrow, i.e. from right to left. The downward-pointingarrows situated above the curve indicate actuations of the operatingpanel 12.

The displacement of the bottom door 7 downward starts with thetwo-handed actuation of the displacement switch panels 25, 26 or of theOPEN switches 25 b or 26 b, as indicated by the perpendicular arrow onthe top left. The control circuit 13 controls the drive motor 9 so thatthe bottom door 7 starts up gently, i.e. with a defined ramp R1, to itstarget speed vL of (in this case) 50 mm/s. The ramp R1 is linear in thiscase. The drive motor 9 is therefore not simply activated.

The displacement movement is therefore also load-independent, inparticular it is independent of the loading of the bottom door 7 orchanges in the frictional conditions of the mechanism. An input variablefor this purpose may be the number of rotations of the drive motor 9.These may be measured by Hall sensors, for example.

Once the target speed vL=50 mm/s is reached the bottom door 7 travelsconstantly downward until it is close to the maximum opening PZ, whichresults from the constructively preset maximum displacement of thebottom door 7 or from the reaching of the work surface 8. In thisdiagram it is assumed that the constructive maximum opening PZ isreached. In this case the control circuit 13 detects this approach and,gently and automatically, slows down the bottom door 7, i.e. with adefined ramp R2, at PZ. The two ramps R1 and R2 may have other gradientsor forms. The approach to the base plate may be detected by end switches33 and/or by monitoring of the displacement path.

If one or both of the displacement switches 25 b, 26 b is released, asindicated by the perpendicular arrow on the top left, the bottom door 7stops abruptly without ramp, as indicated by the dotted arrow. In thismode, therefore, the movement is started gently but halted abruptly,unless the end position is reached.

The cooking space 3 is not opened, and the bottom door 7 is thereforenot displaced from the zero position P0, if an anti-opening safeguard isactive, i.e. if, for example, a defined temperature e.g. 425° C. or 600°F. is exceeded in the cooking space, or if a child safety feature isactivated.

FIG. 7 is a not-to-scale diagram similar to FIG. 6, showing adisplacement of the bottom door 7 from the closed state to a storedposition P1=476 mm in automatic displacement mode.

In this case, as a result of brief activation of one of the OPENswitches 25 b or 26 b, as indicated by the perpendicular arrow on thetop right, the bottom door 7 starts to move automatically to theposition P1. Here, too, the bottom door 7 is started up gently(right-hand ramp) and slowed down automatically (left-hand ramp). Inthis embodiment it is possible, in automatic mode, to select between twofixed target speeds, i.e. 75 mm/s (dashed line) and 50 mm/s (solidline), wherein the lower speed is particularly ideal for elderly users.The slower speed level is preset, e.g. upon delivery. More than twospeed levels or target speeds may also be provided; the free adjustmentof target speed(s) by the user is also a possibility. Ideally it is alsopossible to switch between at least two speed levels of 50 mm/s and 65mm/s, e.g. when an appliance is initialized.

FIG. 8 is a not-to-scale diagram showing a displacement of the bottomdoor 7 from the maximum open position PZ to the zero position P0, i.e.to the closed state, in manual operating mode.

The displacement of the bottom door 7 upward starts with the two-handedactuation of the CLOSED switches 25 a and 26 a, as indicated by theperpendicular arrow on the top left. The control circuit 13 controls thedrive motor 9 so that the bottom door 7 starts up gently from PZ to itstarget speed of vL=50 mm/s, and then travels constantly at this targetspeed (toward the right).

The control circuit 13 detects an approach to the zero position P0 andgently slows down the bottom door 7 in good time beforehand. Now,however, instead of moving downward directly to the zero position P0 bymeans of the linear ramp, the speed-dependent control is switched tocontrol with defined voltage 4 mm before the zero position P0, i.e. bysupplying the motor 9 with a corresponding voltage. This enables maximumpower development to be set if the drive motor 9 is blocked. Thisvoltage varies according to the history of the displacement (loading,frictional conditions, etc.). The 4 mm opening is detected by the pathmeasurement or additionally or alternatively via the end switches 33. Ananti-jamming mechanism can also be dispensed with in the range from P0to P0+4 mm.

If, as in FIG. 6, one or both of the displacement switches 25 b, 26 b isreleased, as indicated by the perpendicular arrow on the top right, thebottom door 7 stops abruptly without ramp, as indicated by the dottedarrow.

FIG. 9 shows a not-to-scale diagram for a displacement of the bottomdoor 7 from a stored position P1=476 mm to the closed state P0 inautomatic displacement mode. In contrast to the manual displacement modeshown in FIG. 8, only one of the CLOSED switches 25 a, 26 a now needs tobe briefly activated, as indicated by the upper perpendicular arrow. Thebottom door 7 then moves similarly to the manner shown in FIG. 7, onlyin the other direction. When the zero position P0 is approached,then—similarly to the situation from FIG. 8—the braking ramp switchesfrom a speed-controlled state to a load or closing force-controlledstate for the last 4 mm opening.

FIG. 10 is a diagram similar to that shown by FIG. 8, in which a jam nowoccurs at a target speed of vL=50 mm/s, as indicated by the upperperpendicular arrow. If, for example, a hand or a pan etc. becomesjammed between the bottom door 7 and the housing 1, the speed of thebottom door 7 drops away since the object prevents any furtherdisplacement. The lift speed is monitored here, for example, by analysisof the sensor signals from the motor shaft, wherein—for example—the timebetween the measurement signals or pulses is analyzed. The motor currentis only monitored in the second instance, this being a somewhat slowermethod. In particular the power that may be generated by the motor 9 fordisplacement is limited, to prevent accidents caused by excessivelysevere jamming (see also FIGS. 12 and 13). The deviation from the targetspeed is detected by the control circuit 13, e.g. by a speed deviationor a temporary change in speed. The bottom door is thereupon reversed sothat the object may be removed; a warning signal, e.g. acoustic, mayalso be emitted. The bottom door 7 thereafter only starts up again uponrenewed actuation of a displacement keypad 25, 26.

To prevent incorrect triggering of a jammed state, e.g. by a change inloading or a change in the running properties of the mechanism, theanti-jamming mechanism, firstly, may be activated only when the bottomdoor 7 has reached its target speed (if a displacement button 25 a, 25b, 26 a, 26 b is first released before this, the bottom door 7 stopsimmediately), and, secondly, a plurality of sensor signals are analyzed,for example to obtain an average figure.

FIG. 11 shows the jammed state (upper perpendicular arrow) during theopening displacement of the bottom door 7 in automatic mode to adestination position P1, in which an object is jammed between the lowersurface of the bottom door 7 and the work surface 8. In this case thejam may be detected via two redundant end switches, which detect aparticularly uneven easing of the load on the bottom door 7, whereuponthe drive motor 9 reverses. The maximum permitted force-time profile(see FIGS. 12 and 13) is thereby not exceeded.

FIG. 12 shows a maximum force F in N that may be applied to the bottomdoor 7 in the event of a jam during the displacement in a closingdirection (i.e. upward), against the elapsed time t in s as a firstforce-time profile FT1.

If a jam occurs at t=0 s the potential closing force is limited to 100N, corresponding to approx. 10 kg, for 5 s. This makes sense, forexample, if the motor 9 is adjusted upward by the control device 13 inorder to maintain the target speed. This ensures, in particular, thatbody parts are not injured. If the bottom door is drawn up for 5 s with(maximum) 100 N, the maximum applicable force is reduced further to 25N, e.g. for 5 seconds. This level of force can be maintainedsubsequently or, for example, reduced further to 0 N. It must bestressed that this force-time profile FT1 shows only the maximumapplicable force, and the force actually applied is usually lower, e.g.if the jam is detected by the control device 13 and the bottom door 7 isreversed accordingly after t=0.5 s, whereupon the applied force isreduced from 100 N to e.g. 0 N.

The maximum force threshold value of 100 N may also apply for otherdisplacement situations.

FIG. 13 shows a maximum force F in N that may be applied to the bottomdoor 7 in the event of a jam during displacement in an opening direction(i.e. downward), against elapsed time t in s as a second force-timeprofile FT2. In this case the drive motor 9 may apply up to 400 N to thebottom door 7 in a first block of t=[0 s; 0.5 s], and thereafter 150 Nat t=[0.5; 5 s] and thereafter 25 N.

Of course, the time intervals and force threshold values of theforce-time profiles FT1, FT2 may be adjusted to the structure and otherbasic conditions.

FIG. 14 shows an exemplary displacement profile for the memorization offunctions, wherein—during the displacement of the door 7—a parameter vrdependent upon the displacement of the door 7 is determined as areference parameter. A reference speed is particularly preferred as thereference parameter vr.

The parameter is determined, in particular, after the cooking applianceis installed and when it is first commissioned, in order to take intoaccount environmental influences at the place of installation. It isparticularly advantageous, however, for the definition of the parameterto be repeated so that environmental influences that change over time oreven internal features of the cooking appliance can also be taken intoaccount. It is particularly advantageous for such a parameter to bememorized with each displacement of the door, particularly each time thedoor is raised, in order—for example—to enable a constantly variableload to be taken into account.

FIG. 14 shows, by way of example, a speed profile of a displacementspeed vL, wherein a speed v in mm/s is shown over a current position Pof the door 7 in mm.

Where numerical details are provided these must be regarded as purelyexemplary.

Starting from an end position PZ, which corresponds to a fully openeddoor 7, the door 7 is raised in the direction of the muffle 5 whilstbeing accelerated. Once a lower interim position pa is reached, the door7 is moved upward with a constant displacement speed vL.

A further function of the cooking appliance may be triggered dependingon the displacement speed vL as an exemplary parameter. Thus, forexample, a jammed state may be detected if the displacement speed isbelow a target displacement speed vR before an upper interim position pbis reached, after which point the door 7 is moved toward the muffle 5with decreasing speed.

The deviation below a permitted minimum speed vS is preferably definedas a criterion for the emission of a jammed signal or the registering ofa jammed state. In principal, however, a fault may also generally bedetected when the speed falls outside a tolerance range vT, wherein thespeed tolerance range vT is likewise preferably preset dependent uponthe current operating conditions.

In the illustrated exemplary displacement profile the jammed statesituation is drawn, in which the displacement speed vL falls off beforethe upper interim position pb is reached and is lower than the permittedtarget or minimum speed vS, as illustrated on the basis of the outlinedjam-speed profile. In such a case the door 7 is preferably acceleratedin the opposite direction (reversed) and moved downward by an openingpath s to enable a jammed object to be removed, as outlined by means ofthe exemplary reset-speed profile v2.

Since the constant speed that may be achieved for the cooking appliancefor raising the door 7 may vary depending on the current load on thedoor 7 and/or depending on current external and internal operatingconditions, the cooking appliance may not be able to reach a normallypermissible minimum speed vS, then—for functions such as, for example,the monitoring of a jammed state—it is preferable for a memorizedparameter, such as the reference speed vr, to be used as the basis asthe reference parameter for a target speed vR that is to be used.

Depending on such a reference parameter, which is determined once, afterinstallation of the cooking appliance or subsequently, as being theparameter to be determined and, in particular, to be measured, apermissible minimum speed vS and/or a speed tolerance range vT are thendefined individually in each case.

The reference parameter, in particular the target speed vR, ispreferably determined after the lower interim position pa is reached,after which point the door 7 moves upward at a constant speed. Thereference speed vr can preferably be determined on an initial pathsection as a reference path sr, so that a parameter determined over sucha reference path may already be used for the continued upwarddisplacement of the door 7.

In principal, however, it is also possible for the parameter to bedetermined over a reference path sr* which is already within theacceleration range of the door 7 between the end position PZ and thelower interim position pa. In particular, such a definition cantherefore be carried out advantageously if—apart from an initialacceleration on start-up and a transition phase to the constantspeed—there is a constant acceleration phase.

In principal, however, it is possible for the reference parameter to bedetermined over a greater range, possibly even over the entiredisplacement path. The inclusion of the entire displacement path,inclusive or exclusive of acceleration or deceleration ranges, may beused in normal operation, particularly for the detection of faults orchanges in the displacement conditions (friction, leverage, etc.). Inthe event of a fault a service signal may, for example, be emitted,which alerts the user to the need for lubrication or maintenance ofguide rails or of a drive module.

When parameters are memorized, such as the reference speed vr as aparameter, a procedure is preferred in which an operator must keep one,or preferably two, buttons 25 a, 26 a, pressed down for the duration ofthe parameter setting process over a specific predefined, particularlyinitial, lifting path of the door 7. For example a user must hold downthe button(s) for at least two seconds when the door is started up,enabling the appliance to reach the ramp or the lower position pa and totravel through the reference definition section sr. If the button(s)is/are released early, the result is that the reference value vr cannotbe correctly determined, which may—for example—lead to an anti-jammingmechanism not being activated on the basis of the displacement speed vL,which is why—in turn—automatic displacement mode is not permitted.Releasing of the button therefore causes the displacement to stop andthe parameter definition process to be aborted. Even in subsequentdisplacement movements, it is preferable for the definition of aparameter to be aborted in the event of a fault, such as—for example—ajammed state, to ensure that no parameters determined on the basis of anincorrect displacement movement are stored.

In addition to the definition of the reference parameter vr, thelatter—as already described above—may also be readjusted by monitoringand adjusting it for small, systematic changes, e.g. due to variablefrictional or leverage conditions, over one or more additional ranges.This readjustment is preferably carried out within the range of aconstant target value, e.g. in the range of a constant displacementspeed.

A parameter may be permanently stored in the cooking appliance uponbeing memorized for the first time. It is useful, however, for such aparameter to be updated from time to time or even with each displacementmovement, so that changing operating conditions are taken into account.

List of reference characters  1 Housing  2 Wall  3 Cooking space  4Viewing window  5 Muffle  6 Muffle hole  7 Bottom door  8 Work surface 9 Drive motor 10 Lifting element 11 Operating element 12 Operatingpanel 13 Control circuit 14 Display elements 15 Cooking hob 16 Heatingelement 17 Heating element 18 Flat heating element 19 Vitroceramic hob20 Retaining part 21 Cooking product carrier 22 Upper heating element 23Fan 24 Seal 25 Displacement switch panel 25a Upward displacement switch25b Downward displacement switch 26 Displacement switch panel 26a Upwarddisplacement switch 26b Downward displacement switch 27 Memory unit 28Confirmation button 29 Main switch 30 Motor shaft 31 Hall element 32Meter 33 End switch FT1 First force-time profile FT2 Second force-timeprofile P Position pa Lower interim position pb Upper interim positionP0 Zero position PZ End position PS Reversing position R1 Speed ramp R2Speed ramp ds Jammed signal sr, sr* Reference paths v2 Reset speedprofile vr Reference parameter (reference speed) vR Target speed vSMinimum speed vT Speed tolerance range vL Displacement speed of bottomdoor

1-12. (canceled)
 13. A cooking appliance, especially a top-mountedcooking appliance, comprising: a muffle that defines a cooking space andis formed with a muffle access opening; a door pivotably mounted to themuffle for movement into and out of a covering relation with the accessopening; a driving device in operative engagement with the door; acontrol device operatively associated with the driving device forcontrolling door movement; and means for determining a door displacementparameter during door movement wherein a determined door displacementparameter is used as a reference parameter for a function of theappliance.
 14. The cooking appliance according to claim 13 and furthercomprising means for using the reference parameter to generate a triggersignal in the control device to initiate action by the driving devicewith respect to door movement.
 15. The method according to claim 13 andfurther comprising means for using the reference parameter as acriterion in subsequent displacement movements of the door.
 16. Thecooking appliance according to claim 13 and further comprising means fordetermining a reference speed of door movement from a displacementspeed, wherein the reference speed is defined as the referenceparameter.
 17. The cooking appliance according to claim 16 wherein thereference parameter is determined after a substantially constantdisplacement speed has been reached by the door.
 18. The cookingappliance according to claim 16 wherein the reference parameter isdetermined after a substantially constant door acceleration has beenreached.
 19. The cooking appliance according to claim 13 wherein thedetermination of the reference parameter is defined over an entire doordisplacement path.
 20. The cooking appliance according to claim 13wherein a jammed state is defined dependent upon the determinedreference parameter.
 21. A method for operating a cooking appliance,especially a top-mounted cooking appliance, comprising the steps of:providing a cooking appliance having a muffle that defines a cookingspace and is provided with a muffle access opening; a door pivotablymounted to the muffle for movement into and out of a covering relationwith the access opening; a driving device in operative engagement withthe door; providing a control device operatively associated with thedriving device for controlling door movement; providing means fordetermining a door displacement parameter during door movementoperatively associated with the control device; determining a parameterdependant on door displacement the determination occurring during doordisplacement; and using the determined parameter as a referenceparameter for a function of the appliance, in particular an anti-jammingfunction.
 22. The method according to claim 21 wherein the step ofdetermining the reference parameter includes holding at least one switchclosed, the switch being operatively associated with the door.
 23. Themethod according to claim 22 and further comprising the step of abortingthe determination step upon early release of the at least one switch.24. The method according to claim 22 wherein in the determination step,the at least one switch is opened prior to determining the referencevalue and automatic operation on the basis of the reference parameter isnot permitted, in particular no displacement operation of the door ispossible.